Bright, I'm sorry to read that your h had his arm around another woman at the race. It could have been a friendly gesture or it could be something totally different. Sounds like she was looking for someone to rescue her from her heartbreak and maybe your h has taken her under his wng. Your h "appears" to be following the script to a "t". He's been a slow one for quite some time and is now being more open about what he's doing, especially around his friends and FB.
Again, I am sorry, but please, don't allow this photo to ruin your holiday. You've come too far to allow his antics to get you down.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.